HANAHAN, S.C.  Sametta Heyward was in a bind. The single mother was scheduled to start a double shift at 3 p.m. and her baby sitter had just canceled.

"She was either told to come to work or be fired or she was afraid to call in sick -- one of those things," said police Lt. Michael Fowler.

She made it to her job at a county-run group home July 29, a typically warm summer day. After eight hours she called a supervisor and said she had to leave because of child-care issues.

According to her employer, she didn't tell the supervisor or a co-worker that for all that time, she had left her 1-year-old daughter and 4-year-old son in her Chevy Cavalier hatchback, parked on a residential street.

She had left Triniti and Shawn with battery-powered fans, food and drinks, but it was not nearly enough to combat the sweltering conditions inside. She later told relatives that when she got to the car at 11:30 p.m., the children were unconscious and had weak pulses.

A day later, police found her at her apartment wailing, "Oh, my babies!"

Officers said in a police report that she tried to kick and bite them and asked them to kill her. The bodies of the children, bathed and dressed, were found wrapped in trash bags and stuffed under the sink.

Heyward, 27, was charged with two counts of homicide by child abuse. A funeral for the children was held Saturday.

Lab tests are pending that could help determine whether the children died in the stifling car or sometime after their mother rushed their limp bodies back to their tiny apartment.

A host of other questions remain unanswered: Why didn't she take the children inside the group home? Did she ever check on them? Why didn't she tell her supervisor the baby sitter had canceled? If the children were alive when she got to them, why didn't she seek medical help?

People who know her say they considered her a loving mother, despite a life that turned tough long before she moved into the 252-square-foot efficiency apartment.

"She and her kids were always happy, smiling and joking," said Tony Smith, who lived a few doors down and often shared meals with the family.

Smith's wife, Sheryce Robertson, would sometimes baby-sit, but Robertson was sick when Heyward asked her to care for the kids that Sunday.

It was an average summer day by South Carolina standards: 88 degrees. But the inside of the car would have been like an oven, according to experts, who say the children may not have had much of a chance even if the windows were cracked.

"If it's in direct sunlight, you can easily get temperatures of 130 or 140 degrees in a car in 10 or 15 minutes," said Dr. Keith Borg, an emergency room physician at the Medical University of South Carolina. "At that kind of temperature it could kill an infant or a small child in minutes."

Her friends and her bosses -- and even the officers who arrested her -- say Heyward had been trying her best: working long hours and providing for her children.

She and her children had moved in May into the $185-a-week apartment in Hanahan, a bedroom community of about 14,000 people some 15 miles from Charleston. She told the apartment complex manager they wouldn't be there long, that she was already looking for another place.

She had been arrested twice in the past three years, but she was not prosecuted on a charge of hindering an officer and was found not guilty of first-degree criminal domestic violence in February 2006.

A few months before the move, she put a newborn up for adoption. A 12-year-old son lives with his father in Maryland.

If those things affected her, it didn't show on the job. In a recent statement, the Disabilities Board of Charleston County said Heyward "was a valued employee who received good evaluations of her work" and was well-regarded by staff and clients.

Her lawyer, Andy Savage, said he hopes a mental evaluation will shed light on what happened.

"Neighbors see her as a great mother. This isn't a woman who beat her kids," he said. "Suppose she went to work that night and left them at home. Would that have been better?"

Attorney Andy Savage talks with Sametta Heyward before her bond hearing Tuesday, July 31, 2007, at Hanahan Municipal Court in Hanahan, S.C.. Heyward, 27, who is accused of leaving her two young children in a hot car while she was at work, was charged with homicide by child abuse after their bodies were found wrapped in trash bags under an apartment sink, authorities said. (AP Photo/Post and Courier, Tyrone Walker)